A/C comes on when sitting in the car with everything turned off

[johnny_cakes]

I'm a new owner of a 2019 Model 3 and I encountered a strange A/C behavior yesterday. My wife was driving and I was in the passenger seat. She parked the car and went into a business meeting while I worked on my laptop in the passenger seat. Outside temperature was 9C (48F) while cabin temperature was a comfortable 20C (68F). Everything was turned off in the car, including climate control. I knew the cabin would slowly cool down, but my wife's meeting was only 1 hour so I was fine with that. After about 5 minutes of being parked, the A/C suspiciously started blowing cold air into the cabin. I looked at the Tesla app on my phone and it showed no indication of climate control activity. I turned climate control on then off from my phone to get the A/C to stop. Then after several minutes it happened again, at which point I had to turn climate control back on then off to get A/C to stop. I had to do this over and over again. It was extremely frustrating and cabin temperature was getting unnecessarily cold (down to 13C (55F) after 8 or so cycles of this. Anyone know what was happening and what I can do to prevent it?

 

[GtiMart]

I believe this is normal. Once you have used the AC and get out of the car, it will automatically run the fan to dry the AC radiator. This is to prevent mildew which eventually causes bad odors. By cycling the AC you turned that off, but since you stopped everything again the car decided to do it a few minutes later.
I believe that if you had tapped the screen to tell the car to stay on, it wouldn't have happened. In fact, since you're there, you can turn on the HVAC and leave it to a comfortable temperature. Contrary to an ICE car, leaving the HVAC on doesn't pollute

 

[johnny_cakes]

Thanks for the reply @GtiMart! That makes sense.

 

[Teslinator]

I am having a similar problem with my 2018 model 3 performance. I am the original owner of this vehicle and the problem with the a/c only just recently started happening.

The a/c has been randomly coming on after I turn the car off and go inside my house. And no, it is not the fan trying to cool down the battery. The A/C system is coming on and cooling down the interior of the car to whatever temperature the climate control is set to for the interior of the car. I have never previously experienced this problem with the car for the last 5 years I have owned it. I am doing nothing different with the operation of the car since I owned it. I have tried doing a reset on the car computer a couple of times but it has not fixed the problem. I am suspecting that it the result of some update or my computer system is somehow now compromised.

I have also have one other weird thing happening. I quite often have find my headlights to my car to still on hours after parking it and coming out back into my garage. The car is in park and locked. This likewise is a new event that recently started happening

Anyone else experiencing this problem or a similar problem and have a solution?

 

[Watts_Up]

I believe this is normal. Once you have used the AC and get out of the car, it will automatically run the fan to dry the AC radiator. This is to prevent mildew which eventually causes bad odors. By cycling the AC you turned that off, but since you stopped everything again the car decided to do it a few minutes later.
I believe that if you had tapped the screen to tell the car to stay on, it wouldn't have happened. In fact, since you're there, you can turn on the HVAC and leave it to a comfortable temperature. Contrary to an ICE car, leaving the HVAC on doesn't pollute

This was described in the videos referenced in this TMC thread:

This design flaw makes Tesla’s Model 3 smell bad!

Interesting video content: This design flaw makes Tesla’s Model 3 smell bad! (Part 2) Here is also the first video: This design flaw makes Tesla’s Model 3 smell bad! (with fixes!)

teslamotorsclub.com

 

[Teslinator]

I do not believe this situation is the fan turning on to dry out the AC radiator. If I last had the AC set to low, when the AC randomly turns on, it operates at the last setting. In the instance where I have it set to low, it will cool the interior of the car down to the high 50s. The AC is actually operating, not just running the fan.